Once again, American leaders find themselves preparing for the possibility of a terrorist attack.

U.S. intelligence officials say al Qaeda is seeking to take revenge for the killing of their leader, Osama bin Laden. Consequently, implementing extra security measures both in America and overseas.

"I think the major issue for al Qaeda is to do something, to prove that they're still alive, to do some fairly major event or series of attacks that prove that they're not down, they're not out," counter-terrorism expert Richard Clarke said.

Click play to watch Efrem Graham's report, followed by more with CBN News Terrorism Analyst Erick Stakelbeck on the threat of al Qaeda following bin Laden's death.

President Obama has been briefed about possible al Qaeda plans for retaliation for bin Laden's death.

Officials say they don't have specific information about an imminent strike, but al Qaeda's top bomb maker, Ibrahim Hassan al-Asiri, has just re-surfaced in Yemen.

Al-Asiri is believed to be responsible for the attempted 2009 "underwear bomb" attack as well as the bombs hidden in printers that al Qaeda tried to ship to Chicago in 2010. American intelligence officials say he could be building more bombs to use against the United States.

"It doesn't take a great number of people to do the kind of attack that we had on September 11," Clarke explained. "That was less than two dozen people and it's clear that they have that number available in places like Yemen today."

Meanwhile, the Obama administration is stepping up the fight against al Qaeda in Yemen, giving the go-ahead for expanded drone attacks against targets there.

In a change in U.S. policy, officials now say individuals who are planning attacks against the United States will be targeted, even if they can't be identified by name. The attacks will be carried out only with Yemeni government approval.

This comes after one State Department official recently told the National Journal, "the war on terror is over."

The source said the Obama administration believes radical Muslims may see the Arab Spring as a new outlet for their Islamism.

Threats of a revenge attack have been monitored by the U.S. ever since the raid last year on bin Laden's compound. Papers were found in his home with repeated references to the importance of attacks that coincide with anniversaries.

Efrem Graham

News Anchor & Reporter

Efrem Graham is an award-winning journalist, who comes to CBN News from the ABC owned and operated station in Toledo, Ohio. He received his master's degree from the Columbia University Journalism School. He also holds a bachelor's degree in English Literature from the Richard Stockton College of New Jersey. Follow Efrem on Twitter @EfremGraham and "like" him at Facebook.com/EfremGrahamCBN.